Method for locating, measuring, and evaluating the enlargement of a foramen

ABSTRACT

A method for locating, measuring and evaluating the enlargement of a foramen are provided. An instrument has a handle, an angled region, and a tip to be inserted into the foramen. An instrument can be pressed onto the foramen to determine its location and whether the empty space within the foramen is large enough for the maximum width of the tip to be inserted. If the tip cannot insert, the foramen can be cut to enlarge it enough for the tip to insert. A kit of several instruments or a single instrument with tips of different maximum widths are provided for determining the amount of empty space within the foramen through the course of the enlargement.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional application of U.S. patent applicationSer. No. 10/301,944, filed Nov. 22, 2002, the disclosure of which isincorporated herein by reference, as if fully stated here, for allpurposes.

FIELD OF THE INVENTION

The present invention is directed to surgical instruments and methods,and more particularly to a system, method and apparatus for locating,measuring and/or evaluating the enlargement of a foramen.

BACKGROUND OF THE INVENTION

Spinal surgeons frequently must work with openings within the body knownas “foramina.” It may be difficult to visualize or to evaluate the sizeor diameter of these foramina, such as, for example, during surgery orif the foramen is very small. In this situation, locating, measuring, orevaluating the enlargement of the foramen can be very difficult. Forexample, the openings where nerves exit the side of the spine, called“neural foramina,” are frequently very narrow. The neural foramen can beparticularly narrow in patients with a common condition known as “spinalstenosis,” where the spinal nerves are compressed by enlarged, arthriticfacet joints. Inability to relieve this narrowing frequently will cause“failure” in back surgery, particularly when the surgery involves“decompression” or opening of the spinal canal and foramina to relievethe pressure on the spinal cord. In some patients, the neural foramen isso small that the surgeon must search to find it before attempting toenlarge it. When found, the surgeon resects pieces of the bonesurrounding the foramen with surgical instruments, such as, for example,“Kerrison” ronguers, until he or she believes that the foramen has beenadequately enlarged around the exiting nerve. This uncertainty aboutwhen the foramen is adequately enlarged frequently results in thesurgeon overestimating the size of the foramen and discontinuing theenlargement prematurely. The greatest number of failures in spinalstenosis decompression surgeries occur because the surgeon has notadequately enlarged the foramen to provide adequate space for theexiting nerve.

Accordingly, a need exists for a system and method of finding andaccurately evaluating the enlargement of foramina in patients undergoingsurgery.

SUMMARY OF THE INVENTION

The present invention is directed to a system, method and apparatus forlocating, measuring and/or evaluating the enlargement of a foramen.

One embodiment of the invention includes a foraminal instrumentincluding a handle, an angular region, and a tip. For purposes of thisdisclosure, the term “handle” refers to a graspable region of theinstrument. In such an embodiment, the tip can be shaped in any mannerthat allows its maximum width to be inserted into the open space in aforamen, for instance, between an exiting nerve and the edge of a neuralforamen. In one preferred embodiment, the tip is substantially roundedor substantially spherical. In such an embodiment, the maximum width ofthe tip of the foraminal instrument can be any size between a size justsmaller than the open space in an unenlarged foramen to a sizeapproximately equal to the desired amount of open space in an enlargedforamen. For example, in a neural foramen, this preferable range wouldbe approximately 0.5 mm to 8 mm.

In another embodiment, the angled region extends at an angle, preferablyabout 60 to 80 degrees, more preferably about 70 to 78 degrees, and mostpreferably about 76 degrees from the tip distally to the axis of thehandle. In such an embodiment, the angled region may be substantiallycurved or substantially linear.

The invention is also directed to a foramen opening system includingmultiple instruments as described above, each having a tip with adifferent maximum width. In an alternative embodiment, the kit includesa single instrument with multiple tips with different maximum widths. Byinserting tips with different maximum widths into the foramen throughthe course of the surgery, a surgeon is able to identify the currentsize or location of the open space in the foramen and how muchadditional enlargement is necessary.

The invention is also directed to a method of evaluating the enlargementof a foramen including locating a foramen in an unenlarged state,pressing an instrument with a tip of a certain maximum width into theforamen, determining whether the tip inserted into the foramen, andcutting away the edge of the foramen if the tip did not insert into theforamen. This procedure can be repeated until the tip of the instrumentinserts into the foramen in an enlarged state.

Another embodiment also includes repeating this method with a secondinstrument with a larger maximum width than the first instrument. Thisallows the foramen to be enlarged in stages, to give the surgeon an ideaof how large the open space in the foramen is throughout the course ofthe surgery, and how much more enlargement is necessary. Finally, inanother embodiment, an instrument with a tip having a smaller maximumwidth is pressed near the foramen until it inserts into the foramen.This allows the foramen to be located before it is enlarged.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features and advantages of the present invention will bebetter understood by reference to the following detailed descriptionwhen considered in conjunction with the accompanying drawings where:

FIG. 1 shows a side perspective view of an exemplary foraminalinstrument, according to one embodiment of the invention;

FIG. 2 shows a enlarged plan view of the tip shown in the embodiment ofFIG. 1 as it is inserted into the neural foramen;

FIG. 3 shows a side view of another embodiment of a system according toone embodiment of the invention; and

FIG. 4 is a flow chart of another embodiment of a method according tothe invention.

FIG. 5 shows a side perspective view of an exemplary two-tippedforaminal instrument, according to another embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

This invention relates to an apparatus, system, and method for locating,measuring and evaluating the enlargement of a foramen to ensure anoptimal surgical outcome. For purposes of this application, the term“foramen” refers to an opening or orifice in the body, more particularlyin the spine, and the term “tip” is the end region of a projectingobject. The term “unenlarged state” for a foramen refers to the size ofthe foramen opening before any enlargement occurs, and “enlarged state”for a foramen refers to the size of the foramen opening after it hasbeen at least somewhat enlarged.

As shown in FIG. 1, one embodiment of the invention includes a foraminalinstrument including a handle 10, an angled region 12, and a tip 14. Thehandle 10 is preferably around 7.5–8 cm long, but one skilled in the artwill recognize that any length that can be comfortably grasped in onehand and that would extend toward the area near the foramen (not shown)would be sufficient. The handle 10 can also be textured or balanced toprovide a better grasp on the instrument, and can include indentations16 on which labels (not shown) and the like may be attached.

The angled region 12 protrudes from the handle 10 at an angle 18. Inthis embodiment, the angled region 12 is curved. It is also within thescope of the invention for the angled region 12 to protrude linearly ata given angle from the handle. The angled region 12 is preferably at anangle 18 of between about 60 to 80 degrees, more preferably betweenabout 70–78 degrees, and most preferably at about 76 degrees from thetip distally to the axis of the handle 10. The thickness of the angledregion 12 near the tip 14 in the embodiment shown in FIG. 1 is narrowerthan the maximum width 20 of the tip 14, to allow at least part of theangled region 12 to insert into the foramen (not shown) with the tip 14.However, in other embodiments, the angled region 12 does not partiallyinsert into the foramen (not shown) and can be of any thickness as longas the maximum width 20 of the tip 14 is narrow enough to insert intothe desired open space in the foramen.

Although the tip 14 in the embodiment of the invention shown in FIG. 1is substantially spherical, it is within the scope of the invention forthe tip to be shaped in any way that would allow it to be inserted intothe open space of a foramen, such as the space in a neural foramen nottaken up by the exiting nerve. For example, the tip may also be rounded,which allows the same approximate size of the empty space in the foramento be determined regardless of slight changes in the orientation of thetip. However, it is also within the scope of the invention for the tipto be in any other shape the surgeon desires.

FIG. 2 shows the angled region 12 of the instrument and the tip 14 fromthe embodiment shown in FIG. 1 in more detail. The tip 14 is showninserted into a neural foramen 100 in the space 106 between an exitingnerve 102 and the edge of the foramen 100. Maximum widths 104 of the tipin some preferred embodiments include: a width equal to the desiredenlarged space [enlarging width] (preferably around 5 to 8 mm, and morepreferably around 6 mm for a neural foramen); a width small enough toinsert in the space 106 before any enlargement is made [inserting width](preferably 0.5 mm to 2 mm, and more preferably around 1.2 mm for aneural foramen); and any intermediate width in between the enlargementand insertion widths to determine an intermediate size of the open space106 and the extent of additional enlargement necessary.

The invention is also directed to a foramen opening system, shown inFIG. 3. In such a system, four instruments 300, 302, 304, 306 with tips310, 312, 314, 316 having different maximum widths 320, 322, 324, 326are included in a surgical kit. The first instrument 300 has a maximumwidth 320 small enough to be inserted into a narrowed neural foramen(not shown) before it is enlarged by the surgeon. The maximum width 320of this tip 310 is preferably around 0.5 mm to 2 mm, and more preferablyaround 1.2 mm for a neural foraminal instrument. The second instrument'stip 312 and the third instrument's tip 314 have intermediate maximumwidths 322, 324 to provide a measure of the extent of foraminal opening.For neural foraminal instruments, the preferred maximum widths 322, 324would be around 2 mm to 4 mm (more preferably 3 mm), and 4 mm to 5 mm(more preferably around 4.5 mm), respectively. The fourth instrument'stip 316 has a maximum width 326 equal to the desired space between theexiting nerve and the edge of the foramen (shown in FIG. 2), preferablyaround 5 mm to 8 mm, more preferably 6 mm for a neural foraminalinstrument. Although four instruments 300, 302, 304, 306 are shown inFIG. 3, a higher or lower number of instruments can be included in thekit to locate and measure the foramen (shown in FIG. 2), depending onthe needs of the surgeon.

Another embodiment (not shown) of a foramen opening system includes asingle handle and an angled region, such as are shown in the embodimentof FIG. 1. However, the embodiment also includes several interchangeabletips (not shown). Each tip can be removably coupled to the angled regionand has one of a selection of maximum widths, as described according tothe embodiment shown in FIG. 4. The tips can be coupled to the angledregion by any means capable of holding the tip in a fixed position, suchas, for example, an angled region with outer threads and a tip withinner threads, etc.

Yet another embodiment of the instrument 10′ shown in FIG. 5, includestwo angled regions 12 a and 12 b fixedly coupled to each end of a handle16. Each angled region is fixedly coupled to a tip 14 a and 14 b havinga different maximum width 20 a and 20 b. This embodiment would allow asurgeon to determine the location and/or size of the foramen at twodifferent stages of the enlargement with the same instrument.

The invention further includes a method of evaluating the enlargement ofthe neural foramen. Referring to FIG. 4, the method includes locatingthe foramen 400, pressing an instrument against the foramen 402,determining if the instrument inserts into the foramen 404, and cuttingthe edge of the foramen 414 if the instrument does not insert 412. Thepressing 402, determining 404, and cutting 414 steps can then berepeated until the instrument inserts into the foramen 406.

In one embodiment, the instrument that is inserted into the foramen hasa tip with a maximum width equal to the desired space between theexiting nerve and the edge of the foramen. Thus, the surgeon can beassured that the foramen is sufficiently enlarged when it is possible toinsert this maximum width into the space and can therefore end thesurgery 408.

In another embodiment, the surgeon repeats 410 this process withmultiple instruments with tips of increasing maximum width in order todetermine the current size of the open space in the foramen during thecourse of enlargement. This method can also be used with one instrumentand multiple fixed or replaceable tips as discussed above. In anotherembodiment (not shown), the step of locating 400 the foramen includesdragging the tip of a foramen locating instrument toward the spine inthe area near the foramen. The tip of the instrument preferably has amaximum width of around 0.5 mm to 2 mm, more preferably around 1.2 mm toensure insertion into the foramen. When the tip inserts into theforamen, the surgeon is able to determine its location. The surgeon canthen begin enlarging the foramen by cutting 414 the foramen's edges.

Although specific embodiments are disclosed herein, it is expected thatpersons skilled in the art can and will design alternate instruments andmethods that are within the scope of the following claims eitherliterally or under the Doctrine of Equivalents.

1. A method for evaluating adequate enlargement of a neural foramencomprising the steps of: providing a first measurement instrument,having a handle, a rigid tip with a first size defined by the maximumwidth of the tip, and a first rigid angled region between said handleand said rigid tip; locating said foramen by manipulating the firstmeasurement instrument within the region of the neural foramen;measuring said foramen by pressing the rigid tip of the firstmeasurement instrument against said neural foramen to determine the sizeof said foramen based on whether the maximum width of the rigid tip ofthe first measurement instrument can be inserted into or through theneural foramen; cutting away at a periphery of said neural foramen ifthe maximum width of the tip of the first measurement instrument cannotbe inserted into said neural foramen; and repeating said locating,measuring, and cutting steps until the maximum width of the tip of saidfirst measurement instrument can be inserted into or through the neuralforamen.
 2. The method of claim 1, further comprising the steps of:providing a second measurement instrument, having a handle, a rigid tipwith a second size defined by the maximum width of the tip that islarger than the first size, and a first rigid angled region between saidhandle and said rigid tip; pressing the tip of the second measurementinstrument against said foramen; determining whether the maximum widthof the tip of the second measurement instrument can be inserted into theforamen; and cutting away at the periphery of said foramen if themaximum width of the tip of the second measurement instrument cannot beinserted into said foramen; and repeating said pressing, determining,and cutting steps with the second measurement instrument until themaximum width of the tip of said second measurement instrument can beinserted into or through the neural foramen.
 3. The method of claim 1,wherein the step of locating further comprises the steps of: providing alocating instrument, having a handle and a rigid tip with a maximumwidth less than an open space in said neural foramen; pressing thelocating instrument near said foramen until the locating instrumentinserts into said neural foramen; determining a location where the tipof the locating instrument inserts into said neural foramen; and usingsaid location to direct the first measurement instrument to the neuralforamen.
 4. The method of claim 1, wherein the rigid tip issubstantially rounded.
 5. The method of claim 1, wherein the rigid tipis substantially spherical.
 6. The method of claim 1, wherein the firstangled region forms an approximately 60 degree to 80 degree angle fromthe rigid tip distally to the axis of the handle.
 7. The method of claim1, wherein the first angled region forms an approximately 70 degree to78 degree angle from the tip distally to the axis of the handle.
 8. Themethod of claim 1, wherein the first angled region forms anapproximately 76 degree angle from the tip to the axis of the handle. 9.The method of claim 1, wherein the first angled region is curved and hasa diameter less than the width of the rigid tip.
 10. The method of claim1, wherein the maximum width of the tip is in the range of approximately0.5 mm to 8 mm.
 11. The method of claim 1, further comprising at leastone substantially rigid substitute tip, wherein the tip and thesubstitute tip are removably coupleable to the angled region.
 12. Theinstrument of claim 1, further comprising a second substantially rigidangled region having a second substantially rigid tip, said secondangled region being coupled to the handle opposite the first angledregion, wherein the second tip and the second angled region are sizedsuch that the second tip is insertable into said neural foramen whensaid neural foramen is in at least one of an unenlarged and an enlargedstate.